Liquid, modified isocyanates produced by reacting methylenebis(phenyl isocyanate) with from about 0.1 to about 0.3 mole of a 134 to 700 molecular weight poly-1,2-propylene ether glycol are known (see, e.g., U.S. Pat. No. 3,644,457). Also known are liquid, carbodiimide group modified methylenebis(phenyl isocyanates) (see, e.g., U.S. Pat. Nos. 3,384,653 and 4,154,752).
Blends of liquid, carbodiimide group modified methylenebis(phenyl isocyanates) with various liquid prepolymers of methylenebis(phenyl isocyanate) are also described in the art (see, e.g., U.S. Patents 4,031,026, 4,065,410 and 4,321,333). Additionally, an isocyanate having an isocyanate group content of about 19% by weight and prepared by reacting (i) methylenebis (phenyl isocyanate), (ii) a carbodiimide group modified methylenebis(phenyl isocyanate) having an isocyanate group content of about 29% by weight and (iii) a 2000 molecular weight polyester diol is commercially available.
Systems are commercially available which are used in o the production of polyurethane shoe soles. In general, these systems comprise a polyether diol, a polyether triol, a chain extender (such as 1,4-butane diol or ethylene glycol), blowing agent, catalyst and surfactant. The use of so-called filled polyols in such systems is described in U.S. Pat. Nos. 4,448,903 and 4,477,602. Although these systems have met with some commercial success, when attempts are made to produce relatively low density parts (such as, e.g., densities in the range of from 0.30 to 0.45 g/cc), low temperature flex fatigue resistance is generally not satisfactory.